The present invention is directed to a composting device and an aerator for use in a receptacle for composting material.
It is becoming a common practice for households to recycle domestic rubbish. One method of recycling is to place organic material, such as food scraps and vegetative matter, in a compost bin, allow the material to decompose and then use the composted material as a fertilizer. A typical compost bin has rigid side walls, an open bottom and top. The bin is placed on the ground so that the ground forms the base of the container. A closure is often provided for the opening.
Unfortunately, the rate of decomposition of material placed in such a bin can be slow as the supply of air to the composting material is often inadequate, especially if the opening to the container is closed with the lid. A free flow of oxygen is essential to support aerobic activity by composting bacteria.
A by-product of decomposition is a fluid called leachate. The present applicant has recognised that 9 this fluid remains in the composting material during the composting process it can interfere with the composting process as it can slow the flow of oxygen in the material. In the type of bins mentioned above it is not possible to easily separate the leachate from the decomposing material, and this is a further difficulty with such bins.
The present application seeks to overcome or ameliorate these problems
According to a first aspect, the present invention is directed to a composting device including:
a receptacle having an opening and an internal space;
load supporting means located inside said receptacle to support material placed therein away from the lower end of the receptacle and to define a fluid collection chamber at said lower end, said fluid collection chamber being in fluid communication with a portion of the internal space above the load supporting means;
one or more aerators located within said receptacle, each aerator having a body having an internal air chamber and one or more apertures to permit air in said air chamber to pass out through said aerator and into said receptacle; and
an air inlet opening into said receptacle and in gaseous communication with said aerator to permit air outside said receptacle to enter said aerator.
The receptacle may be a simple bag. Alternatively, it may be a container having a base, rigid walls and a closure for the opening of the container. A type of container useful in this invention has a pair of wheels located at its lower end and a handle at its upper end so that the container can be tipped onto its wheels and moved around.
Such a wheel container is commonly referred to as a xe2x80x9cwheelie binxe2x80x9d.
Preferably, the load supporting means has an opening and the aerator connects with said opening. For example, the lower end of the aerator may extend into the opening so that there is a contact fit between these two structures.
In this manner the load supporting means also functions to hold the aerator in position, which is preferably in the centre of the receptacle. Where the lower end of the aerator extends through an opening in the load supporting means, a locking nut may be fitted to the lower end to secure the aerator in place.
The lower end of the aerator may have an opening to the internal air chamber aerator. It is also preferably that the upper end of the aerator is closed so as to prevent the entry of composting material into the aerator. However, one or more apertures may be located in the upper end to allow airflow through the upper end.
Preferably the aerator has an elongate shape and is located so that it extends upwards through the centre of the receptacle. It is preferred that the aerator in the receptacle be completely covered by decomposing material so as to minimise heat loss through the aerator. Where the aerator takes the form of a column extending up through the receptacle, and there is insufficient material in the receptacle to completely cover this column, an upper pad of the column, an upper part of the column will be exposed. Accordingly, in a preferred embodiment there is provided a cap for fitting over the upper end of the aerator to minimise the flow of air through the upper end of the aerator.
When the material in the receptacle starts to decompose, heat is generated. The heat causes convection currents in the aerator, which assists in drawing air from outside the receptacle and into the aerator.
In one embodiment a mesh material, such as wire mesh, is used to form the aerator.
In another embodiment, the aerator is formed from one or more interconnecting units, each unit including:
an upper end, a lower end, an internal air chamber and an opening at each upper and lower ends to said air chamber;
one or more projections extending outward from a side of said unit for contacting material failing onto said unit; and
one or more apertures to permit air inside said air chamber to pass through said aerator.
In another aspect, the present invention is directed to such an aerator per se for use in a composting device.
The one or more projections contact compost material falling onto said unit to minimise the build-up of this material around the unit,. Preferably these projections are angled so that they extend downward and outward from the unit and thereby act to deflect material away from the unit. In a further preferred embodiment these deflecting projections are located at or adjacent the upper end of the unit. There may be present only one such angled projection on each unit, which extends around the unit to form a collar. Alternatively, a series of arms may be located around the unit, each arm extending downwardly and outwardly from the upper end of the unit to provide a number of angled surfaces. The arms may form a star or cross pattern when viewed from above. Three to six arms are preferably present. Preferably, the angled surface or surfaces extend to 50 to 100 mm out from the side of the unit.
The outwardly extending projections assist in minimising the compaction of material around each unit as an air gap may form below each projection.
It is preferred that the one or more apertures are located beneath the outwardly extending projections so as to minimise the possibility that downwardly failing material enters the aerator through the apertures. For example, the apertures may be located in the side of the body of the unit. Alternatively, the apertures may be located in the underside of each projection.
The interconnecting units are preferably shaped so that the lower end of one unit can be placed in the upper end of an adjacent unit to provide a contact fit. In this manner, a number of units may be fitted together to form a vertical column. This vertical column will have a series of outwardly extending projections and apertures evenly spaced along its length. This allows a good flow of air into the composting material at appropriate points to optimise aerobic composting and minimises the compaction of composting material.
It is preferred that decomposing material in the receptacle not be able to enter the aerator. Accordingly, where the aerator is formed from interconnecting units as described above, a closure may be provided to close the upper end of the uppermost interconnecting unit. Alternatively, the uppermost unit may differ from the lower units by having an upper end that is closed.
Preferably, the interconnecting units are made from plastics material.
The load supporting. means may be a plate. The surface of the plate may be flat or slightly curved so that leachate from decomposing material that contacts the surface is directed to the perimeter of the plate and then to the fluid collection chamber below. One or more support members may be provided to hold the plate in an elevated position. The function of the plate is to form a platform in the receptacle and create a fluid collection area below. This can be achieved by a load supporting means having different configurations. For example, in another embodiment the load supporting means has a hollow body having an upper surface that forms a platform. Again, support members may be provided. The body and support members may be integral unit. Apertures may be located in the hollow body to allow air flow from outside the receptacle to enter the body and then enter the aerator. In this way the hollow body acts as a bladder.
Retainers may be provided to hold the hollow body in place. Each retainer may be a pin for placement through the air inlet in the receptacle and through an aligned aperture in the hollow body. Preferably, the pin has a bore extending through it to provide an air passage from the air inlet into the hollow body.
It is considered that the combination of load supporting means and aerator is novel in itself. Accordingly, in another aspect, the present invention is directed to a combination of a load supporting means and aerator for placement in a composting receptacle having an internal space, said load supporting means having an upper platform and supports to locate said upper platform in an elevated position and to create a fluid collection area below said platform, said aerator having a body having an internal air chamber and one or more apertures to permit air in said chamber to pass out through said aerator.
The load supporting means and aerator of this aspect may have one or more of the preferred features as described above.
The chamber at the base of the receptacle collects leachate from the decomposing material located above. Leachate is a valuable by-product of the decomposting process and it is therefore advantageous to separate it from composting material for use as a liquid fertilizer. Furthermore, liquid in the lower strata of the decomposing matter can occlude oxygen and turn aerobic decomposition into anaerobic decomposition. For this reason as well, it is desirable to remove the leachate from the body of the decomposing material.
Accordingly, it is preferable to provide an outlet in the fluid collection chamber so that the leachate can be drained. It is also preferable to provide an indicating means to show the level of fluid present in the chamber. This indicating means may be a transparent tube connected to the outlet which, when upturned, acts as a sight glass.
As noted above, the fluid collection chamber is in fluid communication with a portion of the internal space above the load supporting means. This may be achieved by providing apertures in the load supporting means or providing a small gap between the load supporting means and the sides of the receptacle to allow leachate to drain into the fluid collection chamber. It is preferable that the entry of decomposing material into the fluid collection chamber be prevented. This may be achieved by providing apertures of a small diameter or providing a filter over the apertures.
The aerator is in gaseous communication with the air inlet in the receptacle. In one embodiment, an air supply tube may be provided, said tube extending from the air inlet to the aerator. It is further preferred that the tube is made of a rigid material and is located immediately above the load supporting means to assist in holding the load supporting means in position in the lower end of the receptacle.
Where the receptacle is a container having rigid side walls, it is preferably that a bag also be provided to line the inside of the container. The bag performs a number of functions. Firstly, the bag assists in insulating the decomposing material placed in the container. Maintaining the correct temperature in the interior of the container is important to ensure optimum decomposition. The second function of the bag is that it assists in the emptying of the contents of the container. In one embodiment the bag lines the side walls of the container and the bottom of the bag rests on the load supporting means. An opening may be provided in the bottom of the bag through which the aerator extends, Minor apertures may also be provided in the bag to allow leachate to drain from the decomposing material and into the fluid collection chamber below.
To empty the contents of the container, the bag enclosing the decomposing material is simply lifted out of the container. This may be facilitated by attaching handles to the top of the bag.
The material at the bottom of the bag will be in the most advanced state of decomposition. Accordingly, once the bag is removed from the container, it is preferable to invert the bag and remove the material from the bottom of the bag. Where the bag has an opening in its lower end for the aerator to extend through, access to this material may be gained through this opening. It is preferable that the opening be closable. It is also preferable that the opening at the top of the bag is closable to prevent material failing out when the bag is inverted. For example, a drawstring may be provided to close this opening. Alternatively, a flap may be provided around the opening which is folded down when the bag is in use in the container. Prior to lifting the bag out of the container the flap is folded over the opening to close the opening.
When the bag is removed and inverted, it may be preferable to also remove the aerator from the container so that it remains inside the bag. Even when inverted, the aerator should still function to provide air flow to the interior of the bag. Accordingly, the decomposition process can continue in the inverted bag.
Where the receptacle is a container it is preferable that the container has a closure for the opening. This prevents vermin infesting the container and reduces odour escaping from the decomposing material in the container. The closure also minimises heat loss.
Under normal circumstances the generation of heat from decomposing green organic material in a composting container causes gasses to rise and carry moisture through the material. The rising moisture condenses on the closure and in the case of closures found in typical composting bins which are substantially flat, drips back onto the surface of the decomposing material below. This may block the escape of gases and cut off the air flow through the container and consequently kill off aerobic bacterial activity. Furthermore, condensate that drips back onto the composting mass can cool down the mass. It has been realised that decomposition can be improved if the closure is shaped to minimise this return of condensate.
Accordingly, in a preferred embodiment, the container according to this invention has a closure which is configured so that condensate that collects on the underside of the closure is directed to an area external to and/or separated from the internal space of the container thereby minimising return of the condensate to the internal space.
In one embodiment at least part of the underside of the closure slopes towards the perimeter of the closure so that the condensate runs off to the perimeter. For example, part of the underside may have a concave shape. Alternatively, the entire closure can have a dome shape.
It is further preferred that the perimeter of the closure extends beyond the opening of the container when the closure is in place to close the opening. If a rim is present around the opening of the container, this will assist in preventing condensate that collects at the perimeter from entering the interior of the container. A condensate collecting means, such as a channel, may also be provided.
In an alternative embodiment, the underside of the closure has a convex shape. Condensate on the underside runs to the apex of the convex shape and drops onto a condensate collecting means below. This collecting means defines the area separated from the internal space of the container and may be a channel that extends to the exterior of the container. The convex shape may be formed by depression in the upper side of the closure. This depression can also be utilised to collect rainwater. In this case a spout may be provided at the rear of the lid so that when tilted, water in the depression is drained off through the spout and into a separate container. Alternatively, the depression in the lid can be used to hold soil, compost etc.
A further advantage of such closures is that condensate that is removed from the container can be collected and reused for irrigation or other purposes.
Preferably, the closure is hingedly attached to the bin by hinging pins, for example, and is removable from the bin.
In further preferred embodiments the closure has a handle to assist the user to open and close the closure and also to assist in carrying the closure when separated from the container. The closure may incorporate aeration holes to assist in airflow. These holes could be 0.5 to 1.5 mm in diameter and up to five such holes may be provided. These holes prevent build up of dangerous gasses such as methane, in the compost container.
A number of components of the composting device of this invention can be formed from a plastics material which is UV stabilised. Such components include the aerator, load supporting means, retainer and closure. Suitable plastics material base polymer-polypropylene, high density polyethylene or low density polyethylene. The components may be manufactured via injection moulding, blow moulding, rotational moulding, vacuum moulding or fabrication and welding of the plastic material.
Where the receptacle is a container having rigid side wall, it is preferred to provide access in one of these side walls to the interior of the container so that decomposing material can be removed from the container. Preferably, this access is located towards the lower end of the container and above the load supporting means as material in the most advanced state of decomposition will be located in this area of the container. The access may be an opening in the side wall of the container which is closed by a cover such as a hinged flap. It is desirable that this hinged flap seals the opening when closed so as to avoid leakage through the opening.
Decomposing material in the receptacle can be an attractive breeding site for insects. Thus, it is desirable to prevent the entry of insects into the receptacle and this can be achieved by providing filters over all air inlets to the receptacle. Furthermore, an insecticide may be provided in the receptacle to kill any insects that find their way into the interior. Where the receptacle is a container having a closure, a suitable location for the insecticide is the underside of the closure.